The purpose of occupant restraint systems in motor vehicles is for the protection of occupants and to increase their survivability during crash impact of their vehicles. Research and analysis, such as that summarized by Martin Eiband, has identified the acceleration levels adult humans can survive. Eiband was a NASA researcher who published in 1959 a NASA Memorandum entitled "Human Tolerance to Rapidly Applied Accelerations: A Summary of the Literature." The U.S. military commonly uses Eiband data to assess injury survivability levels. Restrained motor vehicle occupants are frequently seriously or fatally injured in crashes that do not exceed these injury tolerance levels. This is usually due to body contact with the interior of the vehicle, vehicle structural intrusion into the occupant space, or non-optimal restraint system loading by the occupant. The subject invention counters these injury mechanisms so that the limiting crash survival factors are human tolerance to acceleration and vehicle intrusion. Occupant restraint systems generally perform three basic functions in order to achieve this purpose: the prevention of occupant ejection from the vehicle, the prevention or minimization of the effects of secondary collisions such as impacts of the occupant with interior vehicular structures, and the control of the crash forces applied to the occupant. Known occupant restraint devices such as three-point lap and shoulder harnesses which perform these functions have been widely researched and improved over the years, thereby significantly increasing automotive safety.
Today, occupant restraint systems in automobiles which typically incorporate the three-point lap and shoulder harness have inherent drawbacks. A properly designed system of this type provides reasonably effective restraint in frontal crashes. Furthermore, when the three-point lap and shoulder harness is coupled with a well-designed seat with sufficient seat back strength, adequate seat back height, and effective geometry, they will also provide adequate occupant protection for rear impact collisions or crashes. However, in crashes having significant lateral and/or vertical components, the effectiveness of the traditional three-point lap and shoulder harness alone significantly diminishes. The diminishment of the protection is especially true if the anchor points of the lap and shoulder harness are mounted to the vehicle rather than to the seat itself or if the principal direction of the force of the crash moves the occupant away from the shoulder harness. A lap/shoulder restraint system does not compensate for this.
Most automobile restraint systems in use today anchor the seat belt system directly to the vehicle structure. This creates a problem with front occupant positions where the seats can be adjusted longitudinally, vertically, and also recline.
These adjustments can result in seat positions that degrade the performance of the three-point lap and shoulder belt harness system. Extensive research has shown that proper anchor location, relative to the occupant, is critical for the optimum performance of the restraint system. Additionally, the design of the seat itself also plays a major role in effectively restraining the occupant. This consideration becomes even more important in vehicles subjected to off-road use such as sport utility vehicles (SUVs), utility vehicles, military vehicles, certain law enforcement vehicles, etc. In these types of vehicles, it is not only important to keep the occupant properly protected during a crash, but to also effectively restrain the occupant when the vehicle is utilized in terrain where, unless the occupant is well restrained to the vehicle through the use of an adequate seat assembly and restraint system, the occupant/driver may easily lose control of the vehicle.
In addition to the safety drawbacks described above, the prior art seating systems which utilize anchoring of the restraint systems to the vehicle itself also imparts economic and logistic drawbacks to the system design in that the entire seating platform becomes more difficult and, perhaps, more expensive to integrate into a variety of vehicles since the anchoring points for the restraints must be individually tailored to the vehicle. Accordingly, it would be desirable and advantageous to have an occupant restraint system which is self-contained on the seating platform which simplifies the integration of the restraint system into a variety of vehicles. Furthermore, it would be advantageous and desirable to have a vehicle safety seat system which effectively overcomes the drawbacks discussed above for typical three-point lap and shoulder harness restraint systems.
Summary of the Invention A vehicle seat assembly for protecting an occupant of a vehicle from injury includes a seat assembly having a seat back and a seat bottom, a pair of side bolsters disposed on each side of the seat back, a combined seat/lap belt and shoulder belt restraint which is affixed directly to the seat assembly, and a secondary shoulder restraint affixed to the seat assembly. The seat bottom includes a front portion and a ramp upwardly sloped towards the front portion of the seat bottom. A cushion constructed of a rate sensitive compression material having a compressive response to a slow application of force and a rigid response to a rapid application of force is disposed adjacent to the seat ramp. Pretensioning devices are operatively connected to both the combined seat/lap belt and shoulder belt restraint and to the supplemental shoulder belt restraint and are adapted to activate in response to a signal from a crash sensor to remove slack from the combined seat/lap belt and shoulder belt restraint and/or the supplemental shoulder belt restraint in all crashes with significant severity.